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//===- PrintSCC.cpp - Enumerate SCCs in some key graphs -------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file provides passes to print out SCCs in a CFG or a CallGraph.
// Normally, you would not use these passes; instead, you would use the
// scc_iterator directly to enumerate SCCs and process them in some way. These
// passes serve three purposes:
//
// (1) As a reference for how to use the scc_iterator.
// (2) To print out the SCCs for a CFG or a CallGraph:
// analyze -print-cfg-sccs to print the SCCs in each CFG of a module.
// analyze -print-cfg-sccs -stats to print the #SCCs and the maximum SCC size.
// analyze -print-cfg-sccs -debug > /dev/null to watch the algorithm in action.
//
// and similarly:
// analyze -print-callgraph-sccs [-stats] [-debug] to print SCCs in the CallGraph
//
// (3) To test the scc_iterator.
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/SCCIterator.h"
#include "llvm/Analysis/CallGraph.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Module.h"
#include "llvm/Pass.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
namespace {
struct CFGSCC : public FunctionPass {
static char ID; // Pass identification, replacement for typeid
CFGSCC() : FunctionPass(ID) {}
bool runOnFunction(Function& func) override;
void print(raw_ostream &O, const Module* = nullptr) const override { }
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesAll();
}
};
struct CallGraphSCC : public ModulePass {
static char ID; // Pass identification, replacement for typeid
CallGraphSCC() : ModulePass(ID) {}
// run - Print out SCCs in the call graph for the specified module.
bool runOnModule(Module &M) override;
void print(raw_ostream &O, const Module* = nullptr) const override { }
// getAnalysisUsage - This pass requires the CallGraph.
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesAll();
AU.addRequired<CallGraphWrapperPass>();
}
};
}
char CFGSCC::ID = 0;
static RegisterPass<CFGSCC>
Y("print-cfg-sccs", "Print SCCs of each function CFG");
char CallGraphSCC::ID = 0;
static RegisterPass<CallGraphSCC>
Z("print-callgraph-sccs", "Print SCCs of the Call Graph");
bool CFGSCC::runOnFunction(Function &F) {
unsigned sccNum = 0;
errs() << "SCCs for Function " << F.getName() << " in PostOrder:";
for (scc_iterator<Function*> SCCI = scc_begin(&F); !SCCI.isAtEnd(); ++SCCI) {
const std::vector<BasicBlock *> &nextSCC = *SCCI;
errs() << "\nSCC #" << ++sccNum << " : ";
for (BasicBlock *BB : nextSCC) {
BB->printAsOperand(errs(), false);
errs() << ", ";
}
if (nextSCC.size() == 1 && SCCI.hasCycle())
errs() << " (Has self-loop).";
}
errs() << "\n";
return true;
}
// run - Print out SCCs in the call graph for the specified module.
bool CallGraphSCC::runOnModule(Module &M) {
CallGraph &CG = getAnalysis<CallGraphWrapperPass>().getCallGraph();
unsigned sccNum = 0;
errs() << "SCCs for the program in PostOrder:";
for (scc_iterator<CallGraph*> SCCI = scc_begin(&CG); !SCCI.isAtEnd();
++SCCI) {
const std::vector<CallGraphNode*> &nextSCC = *SCCI;
errs() << "\nSCC #" << ++sccNum << " : ";
for (std::vector<CallGraphNode*>::const_iterator I = nextSCC.begin(),
E = nextSCC.end(); I != E; ++I)
errs() << ((*I)->getFunction() ? (*I)->getFunction()->getName()
: "external node") << ", ";
if (nextSCC.size() == 1 && SCCI.hasCycle())
errs() << " (Has self-loop).";
}
errs() << "\n";
return true;
}
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